Untitled

How to display the result as a vertical list for this code?
$a= array(implode(", ", $_GET["choice"]));
echo "<table align="center">";
echo "<tr><th>Questions selected </th></tr>";


while (list ($key, $val) = each ($a)) {
echo"<tr><td>";
echo " $val ";
echo "</td></tr>";

}
echo "</table>";

Questions selected :
Explain how to produce the vector image
List THREE of image file types or formats used in multimedia

$a = $_GET["choice"];